The present invention relates to a thermal fixing unit for fixing an image provided on a sheet, and more particularly, the invention relates to the thermal fixing unit for use in a copying machine in which a latent image formed on a photosensitive pressure sensitive sheet is visualized in a developer sheet medium.
In a copying machine, a photosensitive pressure sensitive recording medium carrying thereon a latent image is superposed with a developer sheet medium, and these mediums are pressed together for providing a chromogenic reaction upon rupture of microcapsules on the photosensitive medium. By the chromogenic reaction, a visible image is formed on the developer sheet medium which is then heated by a heat roller etc. for fixing the output image during travel of the developer medium.
In such conventional heating unit, gaseous substance may be released from the developer sheet upon heating, and the gas is discharged out of the heating unit. Such gas has an uncomfortable smell.
A copending U.S. patent application, commonly assigned has been filed bearing Ser. No. 385,376 filed on July 27, 1989. In the copending application, disclosed is a thermal fixing unit in which hot air is blown onto the developer sheet after it is developed. In this thermal fixing unit, also, gas generated may be flowed out of the fixing unit.